1. Field of the Invention
This invention relates to both an apparatus and a process for refurbishing the seat of a valve, and is particularly concerned with refurbishing the valve seats in the steam chest of a turbine generator.
2. Description of the Prior Art
Methods for on-site refurbishment of valve seats are known in the prior art. Such refurbishments must be regularly performed on the valve seats present in the steam chests of turbine generators. The seats of such valves suffer constant exposure to high-pressure steam, as well as frequent impacts from the valve element. The cracks which result in the seats of such valves must be repaired, on the steam chest will in time become ineffective in its ultimate purpose, which is to selectively direct high-pressure steam through the various openings in a manifold-like structure.
One prior art method for the refurbishment of the valve seats in such steam chests consists of the steps of removing the stem and interior mechanism of the governor valve, manually grinding off the sealing layer of metal from the valve seat to be refurbished, manually depositing a new layer of sealing metal around the ground valve seat by means of an arc welder, and then machining the excess metal from the welded deposit of metal until the final desired contour of the rebuilt valve seat is achieved. Typically, all of these grinding and welding steps are carried out by conventional grinding and welding tools which are inserted through the valve stem bore and manipulated by means of makeshift extenders such as broom handles or the like.
Unfortunately, such prior art refurbishing techniques are accompanied by many shortcomings. For example, such procedures are labor-intensive, and hence costly, since a skilled human operator is required at every point in the grinding and welding steps. Additionally, the manipulation of a conventional arc welder through the valve stem bore by means of a makeshift extender renders the operation slow and awkward, and makes it difficult (if not impossible) to uniformly deposit a new sealing layer of metal around the valve seat. Any non-uniformities in this deposit of metal can adversely affect the quality of the resulting refurbished valve seat, which in turn could necessitate more frequent refurbishments.
Clearly, there is a need for both an apparatus and a process for refurbishing the seats of such valves which is inexpensive, convenient and reliable in use. Ideally, such an apparatus and process should minimize the amount of labor necessary to successfully produce a high-quality refurbished valve seat in order to minimize the number of refurbishments necessary over the life of the steam chest.